12DX Coventry Diehead questions

[6ply]

I've had this diehead doing nothing on the bench for some while and decided to see if I could get it working. I should mention that I have never used a Coventry diehead of any description, but I've watched a few videos and seen how they are generally used. I've also got "The Book of the Coventry Diehead" (96 pages) that whilst useful does not reference the model 12DX.

Upon examination the diehead was seized into the thread cutting position (dies, if I had them, would have been closed) but partial disassembly fixed that problem. I can now engage the dies/scroll by rotating the red lever (A) and it locks into position. I had expected the dies would open if the diehead was pulled forward (pulled to the left in my photo) but it does not appear to work that way. The only way I can get the dies to open is to depress the button (B).

Searching online for more information I found this web page:

https://engineering-supplies.com/sub/288/a-coventry-die-heads-dx-type-/

that includes the following text:

New DX Type DieHeads DX die heads are closed with a spring band auot-die closer. They can open either by "pull-off" or "push-off" action, the latter giving a more precise repeatabillity for thread length. The shank is semi-fooating or cushioned. DX heads can be used manually but are designed to be used on automatic machinery especially when producing short fine threads in soft materials.

I'm not exactly sure what they mean by the pull-off or push-off action. Previously I would have expected pull-off to mean the way I have seen die heads used conventionally. e.g. stop feeding the tailstock/capstan and the diehead would disengage automatically. But how about push-off? Is part B meant to hit a stop?

All advice welcome.

 

[6ply]

Just in case anyone is interested in the diehead book:

 

[6ply]

Doh! Taking another look at the manual I believe I may have found the answer. I must have been reading it too late last night and missed this part. The 12DX and X.T.2 look quite similar. If I understand correctly, the diehead must be tripped externally and not pulled-to-trip.

 

[6ply]

 

[Agroshield]

I think you have cracked it. As the manual says, if the standard head is in a turret that indexes rapidly the centrifugal force from the rotation could trip the head.

When it says push or pull, I think your photo shows it as push. The trigger hits a stop at the front of the head, which causes it to trip. I guess that for some parts (e.g. a small diameter thread on a big flange), it would not be possible to put the stop at the front, so it would have to go at the back of the head and operate in the pull mode.

You might have found them already, but Wiseman Threading Tools have a lot of info. on dieheads.

It may be that the products have been renamed since the manual you have was printed.

 

[dan.taylor.1]

If they're of interest I may have some dies to fit that, what do yours measure at?

 

[6ply]

If they're of interest I may have some dies to fit that, what do yours measure at?

Dan, if it had been what I'd previously considered a "conventional" diehead I would certainly have been interested. But it looks like this one won't be much use to me. But thanks for the offer.

 

[dan.taylor.1]

Dan, if it had been what I'd previously considered a "conventional" diehead I would certainly have been interested. But it looks like this one won't be much use to me. But thanks for the offer.

I have a die head too...

I'll grab a pic in a bit!

 

[dan.taylor.1]

Here's what I have.

 

[Erie Fred]

Dan, if it had been what I'd previously considered a "conventional" diehead I would certainly have been interested. But it looks like this one won't be much use to me. But thanks for the offer.

Why not ?
I have both styles, I rigged a holder to position the trip directly under the spindle.
travelling in towards the chuck, it trips on the headstock casting nicely.
You can rig it to be behind the front, at 3'oclock, and rig a simple bracket with all thread
as an adjustable trip rod.

 

[6ply]

Why not ?
I have both styles, I rigged a holder to position the trip directly under the spindle.
travelling in towards the chuck, it trips on the headstock casting nicely.
You can rig it to be behind the front, at 3'oclock, and rig a simple bracket with all thread
as an adjustable trip rod.

Maybe I'll put it back on the shelf. Just in case. I don't think it cost me much, if anything.

 

[6ply]

Here's what I have. View attachment 398744

View attachment 398745

I'll pass for the moment, but thanks.